1. Field of the Invention
The present invention relates to a heat dissipating assembly for removing heat from an electronic package such as a central processing unit (CPU) that is mounted on a circuit board such as a motherboard, and particularly to a heat dissipating assembly which can be easily and securely assembled.
2. Description of the Related Art
With the continuing development of computer electronics technology, new electronic packages such as CPUs can perform more and more functions. Heat generated by these modern electronic packages has increased commensurately. Therefore, bigger and heavier heat sinks are becoming increasingly necessary to efficiently remove the heat from the electronic packages. Higher strength and tension is required for retaining these large heat sinks on the electronic packages.
A conventional kind of heat sink is found in Taiwan Patent No. 086212377 and in U.S. Pat. No. 5,464,054. In this kind of heat sink, a clip made from a single metal wire is positioned in a slot of a heat sink for mounting the heat sink to an electronic package. A plurality of barbs is formed in two sidewalls of the heat sink at the slot, for retaining the clip therein. Two resilient arms extend from opposite ends of the clip in directions substantially perpendicular to each other. A distal end of each arm is bent to form a hook engaging in a corresponding hole of a circuit board on which the electronic package is mounted, thereby fastening the heat sink to the electronic package.
However, the heat sink is prone to be displaced when the assembly is subjected to vibration or shock. Additionally, in assembly, an unduly large force is required to press the clip into the slot of the heat sink. Furthermore, a tool is required for installation or removal of the clip, which makes these processes excessively time consuming. Moreover, the tool is liable to slip during use, which can cause damage to other components on the circuit board. All these difficulties involving assembly retard efficiency in mass production facilities. Reduced efficiency is translated into increased costs.
Thus, a heat sink and fastening assembly which overcomes the above-mentioned problems is desired.
Accordingly, an object of the present invention is to provide a heat dissipating assembly which can be easily and securely assembled.
To achieve the above object, a heat dissipating assembly in accordance with a preferred embodiment of the present invention comprises a CPU mounted on a motherboard, a fan, two clips, a heat sink, two fasteners, a back plate and two posts. The heat sink comprises a base and a plurality of fins. Two ears are formed at respective opposite sides of the base. A fastening hole is defined in each ear. Two slots are defined at two respective opposite sides of the plurality of fins. Each clip comprises a sidewall and a top wall. A retaining portion is formed at a bottom of the sidewall for engaging in a corresponding slot of the heat sink, and two pins depend from the top wall for engaging in corresponding holes of the fan. The clips thus mount the fan to the heat sink. The back plate is placed under the motherboard, and the posts are sequentially extended through the back plate, the motherboard and the fastening holes of the ears of the heat sink. The fasteners are retained on the ears of the heat sink around the respective posts. The fasteners are rotated, causing the posts to resiliently press the fasteners on the ears, and resiliently press the back plate on the motherboard. Thus the heat sink is securely attached to the CPU on the motherboard.